For testing influenza viruses, a rapid test kit is recently used in hospitals and clinics to detect a virus or determine the A/B type using gold colloid particles modified by antibodies. However, the currently used rapid test kit has only a high minimum detection limit. This poses a problem of so-called window period, leading to a failure in obtaining a positive test result in several hours after infection because the multiplication of influenza viruses in the body is still insufficient.
Note that genetic screening can solve the problem of undetected errors caused by the shortage in the minimum detection sensitivity. However, the genetic screening is expensive and time-consuming. There exist apparatuses for detecting the shapes or sizes of fine particles passing through a pore on a one-by-one basis. However, it is impossible to determine viruses having an equal shape or size. Hence, there is presently no apparatus capable of easily detecting a virus or a bacterium in a short time at a high sensitivity.